Electrostatic copier with insertable developer module

ABSTRACT

An electrostatic copier has a rotatable copy drum and a developing unit which can be inserted and removed from the copier in toto. The developing unit is provided with bearing members which at least partly and loosely embrace the shaft of the copy drum.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrostatic copiers.

More particularly, the invention relates to an electrostatic copierhaving a developing station which can be inserted into and removed fromthe copier as a unit.

2. The Prior Art

In electrostatic copiers an original is imaged onto the photosensitivesurface of an endless travelling charge carrier to create a latentelectrostatic image thereon. Toner particles are then attracted to thecharged area of the electrostatic image; i.e. the latent image isdeveloped to form a visible image. The toner particles forming thisvisible image are thereupon transferred to an image carrier, e.g. asheet of copy paper, and fused to provide a permanent image on the same.Various ways of developing the latent image have been proposed,including cascade developing in which the toner material is cascadedover the photosensitive surface of the travelling charge carrier, andmagnetic brush developing. For ease of servicing it is desirable to beable to insert the entire developing station into the machine as a unit,and to remove it in the same manner and such as an arrangement has beenproposed in e.g. German Published Application (DT-OS) 1,961,836.

The quality of the developing process--and hence the quality of thefinished copy--depend to a very large extent upon a precise maintenanceof the position of the developing unit or station relative to the chargecarrier surface; this is important in almost all known developingprocesses, but especially so in cascade developing and magnetic brushdeveloping. To assure such maintenance in constructions in which thedeveloping station is removable as a unit, it has been proposed to usespace rollers which engage the charge carrier surface to maintain thedesired relative position of the station to this surface. However, thecharge carrier surface is highly susceptible to damage and the use ofsuch rollers inherently involves the danger of such damage, which mayoccur e.g. when the charge carrier is removed for inspection orreplacement. To avoid this, the prior art proposes to retract thedeveloping station--together with associated components--out of contactwith the charge carrier surface before the charge carrier is removed.This, however, requires a rather complicated construction which iscorrespondingly expensive.

A somewhat different approach is adopted in German Published Application(DT-OS) 2,436,301 where the removal of the charge carrier is facilitatedby combining it with a surface-cleaning device to form a removable unittherewith. This, however, does not change the fact that in thisconstruction, also, the spacing between the developing station and thecharge carrier surface is maintained by space rollers which must engagethe charge carrier surface.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the disadvantagesof the prior art.

More particularly, it is an object of the invention to provide animproved electrostatic copies wherein the removal and installation ofthe charge carrier is facilitated and the danger of damage to the chargecarrier surface is eliminated, or is at least substantially reduced.

Another object is to provide an improved electrostatic copier whereinthe precise positioning and spacing of the charge carrier surface anddeveloping station relative to one another, is simplified andfacilitated.

A concomitant object is to provide such an improved electrostatic copierwherein the aforementioned objects are attained in a structurally simpleand therefore relatively inexpensive manner.

In keeping with the above objects, and with still others which willbecome apparent hereafter, one aspect of the invention resides in anelectrostatic copier wherein an original to be copied is imaged onto thephotosensitive surface of an endless rotating charge carrier to form alatent electrostatic image thereon which is then developed by attractionof toner particles to the latent image, in a combination which comprisesa housing; a shaft mounting the charge carrier for rotation; and adeveloping unit insertable in toto into the housing to a positionproximal to the charge carrier, the developing station comprisingbearing means which at least loosely embraces the shaft of the chargecarrier.

In the copier according to the present invention the charge carrier,usually a copy cylinder or copy drum, forms with the developing stationa unit which can be inserted into the machine and withdrawn from it, intoto. Any required servicing adjustments can be effected outside thecopier, prior to insertion of the unit into the same.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary, partly broken away side view of a copierembodying the invention;

FIG. 2 is a section taken on line II--II of FIG. 3;

FIG. 3 is a section taken on line III--III of FIG. 2; and

FIG. 4 is a section taken on line IV--IV of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The drawing illustrates in FIGS. 1-4 a single, exemplary embodiment ofthe invention. Since only the illustrated aspects are of importance foran understanding of the invention, the remainder of the copies is notshown and the copier housing is shown only fragmentarily and designatedwith reference character H in FIG. 1.

As shown, the frame 1 of the copier is provided with guide rails 2 and 3for a developer station which can be inserted and removed in toto; thisstation is guided for such movement by rollers 4-7 and has two housingsections 8 and 9 which are connected to one another by screws 18. Thehousing section 8 accommodates the actual developing equipment and thehousing section 9 accommodates a toner metering device.

A shaft 10 is journalled in section 8 for rotation and carries adiagrammatically illustrated magnetic developer roller 11 (known per se)which dips with successive increments of its circumferential surfaceinto a supply of magnetizable toner particles, so that these pafrticlesare attracted to the roller 11 and form thereon a "brush" or "beard".During further rotation of the roller 11 these attracted particles arethen transported to the surface of the charge carrier, which is here inform of a rotating drum 12 mounted on a shaft 13.

A pair of journalling members 14 (only one shown) is mounted on thehousing section 8 by means of screws 15. Each of the members 14 has aforked slot 14a in which axially spaced portions of the shaft 13 areloosely retained. Members 14 are provided with prismatic guides 14b inwhich respective sliders 17 (one shown) are movable. These sliders 17each have a hook-shaped formation 17a which is made to embrace the shaft13 and prevent its disengagement from the slots 14a while the stationhaving the sections 8, 9 is outside the copier. The members 14 arefurther each provided with a recess 14c which embraces, over an angle ofabout 180° , respective anti-friction bearings 19 which are pushed ontothe shaft and journal the same for rotation. These bearings 19 are heldand centered (both with respect to the copier and to the unit) by abearing member 20 which is installed in the copier and engages thebearings 19 when the unit is in inserted (operating) position.

One end portion of the drum 12 is provided with a ring gear 21. Thecopier includes a drive gear 22 with which the ring gear 21 meshes whenthe developing station is in position within the machine, i.e. as shownin FIG. 1. Another gear 23 of the copier meshes with a gear 24 which ismounted on the shaft 10 of roller 11 and which in turn meshes with agear 25 that is mounted on a shaft 16 and provided with an eccentric 26.A torsion spring 28 engages a projection 27 of the frame and reactsagainst a pivot lever 29 to urge an arm 29a of the same into trackingengagement with the eccentric 26. Another arm 29b of the lever 29 tracksan adjustable eccentric 30 which is mounted on a selector disk 31 of thetype which is disclosed in detail in German Application P 26 36 920.0.The disk 31 has its circumference formed with depressions 31a (FIG. 3)for the fingers of a user; it also has detent portions 31b and selectorindicia (e.g. a series of numerals) 31c. The housing section 9 isprovided with a portion 9a which cooperates with the detent portions31b; it also has an indexing mark 9b with which the selector indicia 31ccooperate. Thus, a desired setting of the adjustable eccentric 30 isselected by turning the disk 31 until an indicium 31c corresponding tothe desired setting is located opposite the indexing mark 9b; the disk31 is held in any selected position by cooperation of the portion 9cwith the detent portions 31b. Depending upon the setting selected forthe eccentric 30, the arm 29a can follow the movements of the rotatingeccentric 26 to a greater or lesser extent, so that the lever will pivotto a greater or lesser degree.

To permit such pivoting of the lever 29, the same is journalled on ashaft 32 via a free-wheeling device (one-way coupling) 33. It can thusfreely pivot on the shaft in one direction, but entrains and turns theshaft 32 when pivoting in the opposite direction. As a result, the shaft32 is turned during each to-and-fro pivoting movement of lever 29,through an angular distance which corresponds to the setting selectedwith the disk 31. A toner brush 38 is mounted on the shaft 32 and turnswith the same through corresponding angular distances; the brush 38 thustransports, during each rotation of the eccentric 26, a quantity oftoner through bores 8c in housing section 8 to replenish the tonersupply therein; the amount of toner so transported evidently depends onthe degree of angular rotation of the brush 38. Refilling of the tonerreservoir in housing section 9 can be effected manually, by opening acover 39 which is hinged to a shaft 39a of the section 9.

The bottom of the toner supply compartment in housing section 8 isclosed by a flap-type door 34 which can pivot about a shaft 35 betweenan open and a closed position. It is held in the latter position by grubscrews 36 which are threaded into a turnable rod 37. To open the door 34a user inserts the tip of a screwdriver or another suitable tool into aslot 37a at the outer end of the rod 37 and turns the rod until thescrews 36 assume the broken-line position shown in FIG. 2, thusreleasing the door 34 for movement. The purpose of providing screws 36,rather than non-adjustable elements, is to permit adjustment of thedistance a between the door 34 and the roller 11, since precise settingof this distance is important for proper operation of the developingstation.

Another distance which is important for the same reasons, is thedistance b from the roller 11 to the charge carrying surface of the drum12. To permit this latter distance to be adjusted, the mounting element14 is shiftable along the elongated slots 14d through which the screws15 extend, once the screws 15 are backed off. The distance b can then beprecisely set before the unit is inserted into the copier; of course,since during such adjustment the bearings are not held by the bearingmember 20 a corresponding element must be temporarily used to performthe holding function.

The section 9 has a shaft 41 on which a handle bracket 40 is providedwhich extends over the entire width of the unit. The bracket 40 hashooks 40a and 40b which engage behind cam portions 2b, 3b of members 2a,3a that are mounted on the rails 2, 3. Thus, a movement of the bracket40 in the direction of arrow A produces, via the cam portions 2b, 3b, aclosing movement in direction of the arrow B which results in movinggear 21 into mesh with the gear 22, moving the gear 23 into mesh withthe gear 24 and moving the bearing portions 14a and 20 to closed(journalling) position. The unit is now arrested and ready foroperation.

The exemplary embodiment of FIG. 1 is susceptible of variousmodifications which are intended to be encompassed within the concept ofthe invention. For example, the journals for the shaft of the drum 12need not merely be of two parts (i.e. portions 14c and 20) but couldhave more than those. The portions 14c and 20 also need not necessarilyembrace the outer races of the bearings for shaft 13, in the mannershown in the drawing. Slider 17 could be replaced by another elementwhich retains the shaft 13 in the slots 14a in a different manner.Bracket 40 need not extend over the entire width of the unit and couldbe replaced by a differently shaped and/or acting element.

Furthermore, the gear 23 could be used to rotate the drum 12 in additionto meshing with the gear 24, although the use of the separate gear 22 iscurrently preferred. It is also advantageous if the gear 22 is driven bythe drive for an optical scanning device (known per se) which scans theoriginal to be copied, since such an arrangement will assure minimumvibration in the gear train connecting the optical scanner (if the sameis of the strip-scanning movable type) or the transporter for theoriginal (in which case the scanner is of the stationary type) with theadvancing charge carrier (e.g. the rotating drum 12). Such freedom fromvibration (to at least the maximum possible degree) is of importance forthe quality of the scan.

While the invention has been illustrated and described as embodied in anelectrostatic copier, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. In an electrostatic copier whereinan original to be copied is imaged onto the photosensitive surface of anendless rotating charge carrier to form a latent electrostatic imagethereon which is then developed by attraction of toner particles to thelatent image, a combination comprising a housing; a shaft mounting thecharge carrier for rotation; and a developing unit insertable in totointo said housing in a position proximal to the charge carrier, saiddeveloping station comprising bearing means which embraces said shaft ofthe charge carrier.
 2. A combination as defined in claim 1; and furthercomprising means on said developing unit for removably retaining saidshaft in engagement with said bearing means.
 3. A combination as definedin claim 1, said bearing means comprising first bearing members whichembrace said shaft over at most 180° of arc; and further comprisingsecond bearing members mounted in said housing, each cooperating withone of said first bearing members and each also embracing said shaftover at most 180° of arc.
 4. A combination as defined in claim 1, saiddeveloping unit comprising a housing having two housing sections, one ofsaid housing sections being formed with a pair of forked slots eachhaving an open end and accommodating a length of said shaft; and meansfor retaining said shaft in the respective slot.
 5. A combination asdefined in claim 4, said retaining means comprising for each slot aslide member which is slidable across and retractable from thecross-section of the respective slot.
 6. A combination as defined inclaim 1, said bearing means comprising at least two first bearingmembers; further comprising at least two second bearing members eachcooperating with one of said first bearing members and embracing saidshaft when said unit is inserted in said housing; and means forarresting said unit when the same is inserted in said housing and forconcomitantly closing the first and second bearing members about saidshaft.
 7. A combination as defined in claim 6, said unit having indirection normal to its path of movement into and out of said housing apredetermined width; and wherein said arresting means comprises a handlebracket extending over substantially said predetermined width.
 8. Acombination as defined in claim 1; further comprising a drive gearmounted in said housing; and a driven gear mounted on said unit andarranged to mesh with said drive gear in reponse to insertion of saidunit into the housing.
 9. A combination as defined in claim 1; furthercomprising a drive gear for the charge carrier mounted in said housing,and a driven gear on the charge carrier and arranged to mesh with saiddrive gear in response to insertion of said unit into the housing.
 10. Acombination as defined in claim 1; said unit comprising a tonerreservoir, and means for forwarding successive quantities of toner fromsaid reservoir to the charge carrier.
 11. A combination as defined inclaim 10, wherein said forwarding means comprises a toner transportingroller mounted for rotation, a driven shaft in said unit, an eccentricon said driven shaft, and a swing lever mounted on said tonertransporting roller and coupled thereto via a one-way clutch, said swinglever having an arm tracking said eccentric so as to be swung in a senseimparting angular movement to said toner transporting roller in responseto rotation of said eccentric.
 12. A combination as defined in claim 11;further comprising means for limiting the degree of swinging of saidlever.
 13. A combination as defined in claim 11; further comprisingadjustable means for limiting the swinging of said lever to a selectabledegree.
 14. A combination as defined in claim 13, wherein saidadjustable means comprises an adjustable eccentric engaging another armof said lever.
 15. In an electrostatic copier wherein an original to becopied is imaged onto the photosensitive surface of an endless rotatingcharge carrier to form a latent electrostatic image thereon which isthen developed by attraction of toner particles to the latent image, acombination comprising a housing; a shaft mounting the charge carrierfor rotation; a developing unit insertable in toto into said housing ina position proximal to the charge carrier, said developing stationcomprising bearing means including at least two first bearing membersembracing said shaft of the charge carrier; at least two second bearingmembers each cooperating with one of said first bearing members whensaid unit is inserted in said housing; and at least two anti-frictionbearings each mounted on said shaft and having an outer race which isembraced and held by a respective pair of cooperating first and secondbearing members.